Structures which in their installed configuration have substantial lengths of elongation are often referred to as a mast. Classical examples are masts to support antenna, solar panels, reflectors, and the like. The utility of such structures goes far beyond these uses. Other examples are for keels, spines, and spans. All such applications are referred to herein as "masts".
A pervasive problem with masts is that the dimension of their deployed or elongated configuration makes the mast almost impossible to transport in that configuration. For many land-based applications the solution is quite simple. The mast is provided as a group of individual parts which are joined together at the site.
There are many applications where this solution is not appropriate, because the total bulk takes up too much volume. This is especially true for space-borne equipment and battle field antenna.
To overcome this problem, numerous arrangements have been proposed in which for storage and transport the mast is pulled into its retracted configuration, which occupies a relatively small volume and has a much reduced axial length. It is released from its retracted configuration and in one way or another is caused to extend to its deployed configuration. This available change in bulk volume and axial length enables a long mast to be carried in a small cannister, and to be deployed only when needed.
Attempts have been made to make masts both deployable and retractable, and many of these have been quite acceptable. However, masts of this type when deployed include three or more longerons, often a number of brace members, and always a number of diagonal members to hold the longerons and brace members in an assembled condition. This situation has been faced and to a degree settled by making some parts flexible, especially the diagonals. Also, in some devices the longerons are flexible and continuous, and are stored in a coiled condition. Some rigid members are provided, but in any event the whole assembly is not made up of rigid members. In other applications, the longerons may be jointed together. In both situations it is usual to provide diagonal members in each bay which bay is bounded by two longerons which are flexible.
Again, for many installations these previous efforts are fully suitable. However, flexibility of material generally involves the complication that it will be insufficiently resistive to very high temperatures such as may be imposed under untoward and unusual situations, and the flexible material will not be sufficiently survivable. The consequence is that in such an event, a deployed mast could be disabled by the destruction of its flexible members.
The problem remains to provide a mast which is readily deployable and retractable to about 15% of its deployed length, but which while deployed can withstand extraordinary temperatures as high as 4,500 degrees F. and survive as a viable structure. This invention provides these advantages, using only rigid structural elements, except that after the untoward event it will no longer be retractable. Still it will function for its intended deployed purpose. Under the circumstances this is all that can be expected. All the while, until that event, the mast will enjoy as much retractability and deployability as masts which must incorporate less resistive flexible components.